A robust technological enforcement of digital rights management (DRM) licenses assumes that prevention of direct access to the raw bit stream of decrypted digital content and that license enforcement mechanisms themselves is possible. However, this is difficult to achieve on an open computing platform such as a personal computer (PC).
PCs have been found to be difficult to make robust for maintaining confidentiality of sensitive code and data. Current methods of maintaining confidentiality of code or securing data include existing software based solutions that rely on anti-debugging, integrity monitoring, and obfuscation techniques to deter reverse engineering and tampering. Another technique involves authenticating software code and/or data constants that the system wishes to execute at load-time during a secure boot process. This may be accomplished, for example, via a signature verification technique as recognized by those having ordinary skill in the art. But load-time authentication techniques also suffer from drawbacks. For example, in this technique, the authentication only takes place once, during the secure boot process. Thus, a system utilizing a load-time authentication technique is susceptible to programming attacks and/or data corruption at run-time, where run-time is recognized as being the time period immediately following load-time (i.e., after the secure boot process).
Existing computing systems often attempt to protect the integrity of data stored in registers by implementing a credential-based security system. In such a system, access to registers (i.e., locations in memory that can be read/written) is restricted to those functions (i.e., software programs) whose credentials are verified. This verification may be accomplished by logic within the computing system. However, credential-based security systems suffer from a number of drawbacks. For example, credential-based security systems are only capable of enforcing one data-access policy. Specifically, a function with viable credentials will be permitted to access the data within the register while a function without viable credentials will be denied access to the data. Because these systems rely solely on credential-based verification as a mechanism for data access, they are susceptible to a scenario where a rogue function improperly obtains viable credentials and is therefore permitted to access the data sought to be protected. Furthermore, these systems assume that credential-based data access is the appropriate security policy for all types of data sought to be protected. However, it is often desirable to protect different types of data with different access policies.
Known techniques, such as those discussed above, are frequently not sufficient for use in DRM systems when they are implemented in software targeted to run on a regular PC. There are many tools available to make reverse engineering possible.
Additionally, in a PC, the protection architecture and the access control model of operating systems makes them cumbersome for use as a platform for a DRM content rendering client, because it is difficult to protect sensitive software code with an open architecture. Current methods to maintain confidentiality have been proven to be effective against casual hackers at the expense of high computational and power overhead. But high value assets are still difficult to guard against professional hackers. Therefore, there is a need to provide a secure execution environment in a personal computing environment for the execution of sensitive code and data.